Body Mapping Template + API Gateway

Question

So I'm trying to set up a basic POST to a API Post Method I made that's connected to a simple dynamodb. I have the following Body Mapping Template below:

{ 
"TableName": "bars",
"Item": {
  "barid": {
    "S": "$input.path('$.barid')"
  },
  "phone": {
    "S": "$input.path('$.phone')"
  },
  "location": {
    "S": "$input.path('$.location')"
  },
  "happyhour": {
    "L": [
      {
        "M": {
          "Time": {
            "S": "$input.path('$.Time')"
          },
          "Deal": {
            "S": "$input.path('$.Deal')"
          },
          "Day": {
            "S": "$input.path('$.Day')"
          }
        }
      },
      {
        "M": {
          "Time": {
            "S": "$input.path('$.Time')"
          },
          "Deal": {
            "S": "$input.path('$.Deal')"
          },
          "Day": {
            "S": "$input.path('$.Day')"
          }
        }
      },
      {
        "M": {
          "Time": {
            "S": "$input.path('$.Time')"
          },
          "Deal": {
            "S": "$input.path('$.Deal')"
          },
          "Day": {
            "S": "$input.path('$.Day')"
          }
        }
      },
      {
        "M": {
          "Time": {
            "S": "$input.path('$.Time')"
          },
          "Deal": {
            "S": "$input.path('$.Deal')"
          },
          "Day": {
            "S": "$input.path('$.Day')"
          }
        }
      },
      {
        "M": {
          "Time": {
            "S": "$input.path('$.Time')"
          },
          "Deal": {
            "S": "$input.path('$.Deal')"
          },
          "Day": {
            "S": "$input.path('$.Day')"
          }
        }
      },
      {
        "M": {
          "Time": {
            "S": "$input.path('$.Time')"
          },
          "Deal": {
            "S": "$input.path('$.Deal')"
          },
          "Day": {
            "S": "$input.path('$.Day')"
          }
        }
      },
      {
        "M": {
          "Time": {
            "S": "$input.path('$.Time')"
          },
          "Deal": {
            "S": "$input.path('$.Deal')"
          },
          "Day": {
            "S": "$input.path('$.Day')"
          }
        }
      }
    ]
  },
  "name": {
    "S": "$input.path('$.name')"
  }
}
}

Here is what I'm testing the post statement with:

{
"barid": {
    "S": "005"
},
"happyhour": {
    "L": [{
        "M": {
            "Time": {
                "S": "11AM-9AM"
            },
            "Deal": {
                "S": "$3 Mimosas; $3 Bloody Marys"
            },
            "Day": {
                "S": "Sunday"
            }
        }
    }, {
        "M": {
            "Time": {
                "S": "4PM - 9PM"
            },
            "Deal": {
                "S": "$4 Margaritas, Corona, Corona Light; $3 Bud Light Lime"
            },
            "Day": {
                "S": "Monday"
            }
        }
    }, {
        "M": {
            "Time": {
                "S": "4PM-9PM"
            },
            "Deal": {
                "S": "1/2 Price Burgers; $2 Bud and Bud Light Drafts"
            },
            "Day": {
                "S": "Tuesday"
            }
        }
    }, {
        "M": {
            "Time": {
                "S": "4PM-9PM"
            },
            "Deal": {
                "S": "$2 Drafts; $3 Food Menu"
            },
            "Day": {
                "S": "Wednesday"
            }
        }
    }, {
        "M": {
            "Time": {
                "S": "4PM-9PM"
            },
            "Deal": {
                "S": "$2 Beers, House Liquor, Flavored Vodka; 1/2 Price Wings; $5 Pizzas or Pasta Bowl"
            },
            "Day": {
                "S": "Thursday"
            }
        }
    }, {
        "M": {
            "Time": {
                "S": "4PM-9PM"
            },
            "Deal": {
                "S": "$5 Red Bull House Liquor Cocktails; $5 Wings, Nachos, Sliders, Flatbreads; $5 Finlandia Cocktails and Martinis; $15 Sam Adams Light Buckets"
            },
            "Day": {
                "S": "Friday"
            }
        }
    }, {
        "M": {
            "Time": {
                "S": "None"
            },
            "Deal": {
                "S": "None"
            },
            "Day": {
                "S": "Sunday"
            }
        }
    }]
},
"phone": {
    "S": "[phone]"
},
"location": {
    "S": "3100 Clarendon Blvd, Arlington, VA 22201"
},
"name": {
    "S": "Mister Days"
}

}

Whenever I run this it seems that it populates the barid, phone and location field but leaves the happyhour array blank. Below is what I got in the logs after running the test.

"TableName": "bars",
"Item": {
  "barid": {
    "S": "{S=005}"
  },
  "phone": {
    "S": "{S=[phone]}"
  },
  "location": {
    "S": "{S=2500 Hess Road}"
  },
  "happyhour": {
    "L": [
      {
        "M": {
          "Time": {
            "S": ""
          },
          "Deal": {
            "S": ""
          },
          "Day": {
            "S": ""
          }
        }
      },
      {
        "M": {
          "Time": {
            "S": ""
          },
          "Deal": {
            "S": ""
          },
          "Day": {
            "S": ""
          }
        }
      },
      {
        "M": {
          "Time": {
            "S": ""
          },
          "Deal": {
            "S": ""
          },
          "Day": {
            "S": ""
          }
   [TRUNCATED]
Thu Jun 30 15:36:27 UTC 2016 : Endpoint response body before transformations: {"__type":"com.amazon.coral.service#UnknownOperationException"}

Not sure what I'm doing wrong but anything would help. Thanks!

Answer 1

It looks like happyhour contains an object with a single attribute named L which contains an array of object. You'll probably want to loop over the array so that your mapping template will still work regardless of the length of the array. You also need to reference items in the input by their full path, not just their name.

It should look something like this...

#set($inputRoot = $input.path('$'))
{ 
"TableName": "bars",
"Item": {
  "barid": {
    "S": "$inputRoot.barid.S"
  },
  "name": {
    "S": "$inputRoot.name.S"
  },
  "phone": {
    "S": "$inputRoot.phone.S"
  },
  "location": {
    "S": "$inputRoot.location.S"
  },

  "happyhour": {
    "L": [
#foreach($elem in $inputRoot.happyhour.L)
      {
        "M": {
          "Time": {
            "S": "$elem.M.Time.S"
          },
          "Deal": {
            "S": "$elem.M.Deal.S"
          },
          "Day": {
            "S": "$elem.M.Day.S"
          }
        }
      }#if($foreach.hasNext),#end
#end
    ]
  }
}

Note that the mapping template order and the output order do not have to match the input order. Also, you don't have to keep the exact same structure. You could, for example, remove all of the extra type information and output cleaner json like this...

#set($inputRoot = $input.path('$'))
{ 
"TableName": "bars",
"Item": {
  "barid": "$inputRoot.barid.S",
  "name": "$inputRoot.name.S",
  "phone": "$inputRoot.phone.S",
  "location": "$inputRoot.location.S",
  "happyhour": [
#foreach($elem in $inputRoot.happyhour.L)
      {
          "Time": "$elem.M.Time.S",
          "Deal": "$elem.M.Deal.S",
          "Day": "$elem.M.Day.S"
      }#if($foreach.hasNext),#end
#end
  ]
}

Answer 2

This might not be right approach if you really want to do the mapping in the API, but you can leave the problem up to aws-sdk.

You can create a simple lambda function between your API and dynamoDB. Using there some of the methods provided by Aws: http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB/DocumentClient.html

I tackled a similar issue with this function:

var AWS = require("aws-sdk");

var docClient = new AWS.DynamoDB.DocumentClient();
var tableName = "tableName";

var saveData = function (data) {

  var params = {
    TableName: tableName,
    Item: data
  };

  docClient.put(params, function (err, data) {
    if (err) {
      console.error("Unable to add item. Error JSON:", JSON.stringify(err, null, 2));
    } else {
      console.log("Added item:", JSON.stringify(data, null, 2));
    }
  });

};

exports.handler = function (event) {
    saveData(event);
};